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Re: [pygame] Formal definitions for the BLEND operations

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Subject: Re: [pygame] Formal definitions for the BLEND operations
From: Brian Fisher <brian@xxxxxxxxxxxxxxxxxxx>
Date: Tue, 10 Feb 2009 12:08:02 -0800
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Pin to 0 and 255. Don't roll over.

Or is there something else?

On Tue, Feb 10, 2009 at 11:11 AM, Lenard Lindstrom <len-l@xxxxxxxxx> wrote:

Hi,

I am trying to write unit tests for the blit blend operations and am running into problems. There are no formal definitions as to what exactly a BLEND_ADD, BLEND_SUB and BLEND_MULT do. Sure they are add, subtract and multiply. But what happens with overflow and underflow. Do they truncate or just return maximum or minimum values. I will not look as the source for the answers because then I would just write the tests to pass rather than making tests that reflect the original intent of the operations.

Lenard

--
Lenard Lindstrom
<len-l@xxxxxxxxx>

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